The results summarized below were obtained in collaborative studies. Lack of M2 receptors impairs some cognitive functions but enhances attention in mice Muscarinic receptors are known to play key roles in learning and memory, and reduced muscarinic cholinergic neurotransmission is associated with normal ageing processes and Alzheimer's disease. However, it remains unclear which specific muscarinic receptor subtypes are involved in these functions. In this study, we tested M2 receptor KO mice for visual discrimination, behavioral flexibility, object-location associative learning, attention and response control. Interestingly, we found that M2 receptor deficiency caused improved attentional performance, but significant deficits in several learning and memory tests. These data suggest that M2 receptor activity has divergent effects across different cognitive domains. Our findings also indicate that muscarinic drugs should be assessed across a wide range of cognitive tests, since they may enhance some cognitive functions, but impair others. (Romberg C, Bartko S, Wess J, Saksida LM, Bussey TJ. Impaired object-location learning and recognition memory but enhanced sustained attention in M2 muscarinic receptor-deficient mice. Psychopharmacology (Berl) 235, 3495-3508, 2018) Importance of the M1 muscarinic receptor for retinal neuron survival in aging mice Previous work suggests that muscarinic receptors have potential neuroprotective functions in glaucoma. Studies with aged M1-M5 receptor KO mice showed that the numbers of retinal ganglion cells and axons in the optic nerve were markedly reduced in mice lacking M1 receptors. We also found reduced expression of several antioxidative enzymes and increased levels of reactive oxygen species in the retinal ganglion cell layer of aged M1 receptor KO mice. These data suggest that M1 receptor deficiency cause retinal ganglion cell loss in aged mice due to enhanced oxidative stress. We propose that M1 receptor agonists may become therapeutically useful to promote retinal ganglion cell survival. (Laspas P, Zhutdieva MB, Brochhausen C, Musayeva A, Zadeh JK, Pfeiffer N, Xia N, Li H, Wess J, Gericke A. The M1 muscarinic acetylcholine receptor subtype is important for retinal neuron survival in aging mice. Sci Rep 9:5222, 2019)